Dissertations, Theses, and Capstone Projects

Date of Degree

2-2026

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Chemistry

Advisor

Stephen O'Brien

Advisor

Sanjoy Banerjee

Committee Members

Alexander Couzis

Steven G Greenbaum

Subject Categories

Ceramic Materials | Inorganic Chemistry | Materials Chemistry | Nanoscience and Nanotechnology | Other Chemical Engineering | Other Materials Science and Engineering | Transport Phenomena

Keywords

Batteries, Energy Storage, Calcium Zincate, Grid Scale Storage, Secondary Alkaline Batteries, Aqueous Batteries

Abstract

Rising global demand for energy consumption is expected to ramp up due to the increasing need for data centers for AI and the electrification of commercial and residential processes. This increase in demand comes at a time when we have aging electrical grid infrastructure that is also costly to maintain and expand so grid scale energy storage can help supplement the capacity of the grid. Currently lithium-ion batteries play a pivotal role in many of the rechargeable batteries that are used for personal devices, electric vehicles, and grid scale energy storage due to their explosion in popularity and dropping costs. As the demand for the materials needed for Li-ion batteries grows, there is also an increasing supply chain risk that we face since these materials only come from a few countries in the world and there may not be enough to meet all the demand required in the future. We begin to look towards other battery chemistries beyond lithium such as zinc based batteries which have been widely used as single use disposable AA/AAA batteries for the longest time. Rechargeable alkaline zinc (Zn) batteries are attractive due to their global abundance and inherent safety when using alkaline electrolyte; however limited reversibility currently hinders their widespread commercial viability. Calcium zincate (CaZn2(OH)6∙2H2O, CaZn) is a promising material that has shown improvement vs Zn/ZnO electrodes by allowing higher Zn utilizations at comparable cycle life, making it a promising alterative that can help drive down costs by increasing Zn utilization.   In Chapter 3, additions of CaZn to Zn anodes for rechargeable alkaline batteries were investigated and found to increase cycle life at high 50% Zn utilization of the anode’s theoretical capacity, thereby significantly reducing anode costs. A spectrum of anode formulations with increasing CaZn (0%, 30%, 70%, 100%) in mixtures with metallic Zn is investigated along with minor additions of Bi2O3, acetylene carbon, and CTAB. The total molar zinc content is normalized; thus, electrode capacity is kept comparable, resulting in electrodes relevant to real world use cases. At a high 50% utilization rate, pure CaZn anodes achieved approximately 280 cycles, a five-fold improvement over the 50 cycles of the Zn anodes. This increased efficiency translates to a 25% reduction in cost per cycle. Microscopic analysis reveals that CaZn delays failure by slowing the formation of a passivating zinc oxide layer and reducing "shape change" by keeping zinc and calcium intimately mixed during cycling.   In Chapter 4, we show that despite these gains that can be achieved using pure CaZn anodes, performance eventually fades due to the segregation of Zn from Ca. As these materials separate, zinc migrates toward areas of higher conductivity, leading to increased internal resistance and heterogeneity within the electrode. Results indicate that CaZn performance is highly sensitive to the charge/discharge c-rates; for instance, fast cycling (1C/1C) maintains a 97.5% Coulombic efficiency with 2.5% overcharge, whereas slower, long-duration cycling (C/10:C/100) drops to roughly 65%. The optimal conditions that allow for the highest cycle life have been CaZn at C/3 with 50% Zn utilization, providing ~400+ cycles before capacity fade of 70% of the cycled 50% Zn utilization. These failure mechanisms highlight the critical role of maintaining material homogeneity and optimized charge/discharge rates.   In Chapter 5, to further improve cycling stability and extend cycle life, experiments into additives for conductivity, moisture-retention agents, and excess calcium hydroxide were investigated. What we show is that there is a minimum amount of conductive additive that needs to be dispersed throughout the CaZn electrode to have that a precise level of conductivity is required to sustain performance and other additives would have to be in addition to the conductive additives. This thesis provides a clear roadmap for understanding how CaZn cycles in Zn electrodes and as a pure electrode while optimizing cell fabrication and design, additives, and cycling conditions. These results provide insight into how CaZn based batteries could be designed for commercial applications as a promising alternative to Zn and ZnO based electrodes.

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